DESCRIPTION: (Applicant's Abstract) This competitive renewal proposal is directed at determining which cells from the mouse and human immune systems express mu, delta, and kappa opioid receptors. Studies are further directed at determining if drug abuse, HIV infection and AIDS alters the number of distribution of opioid receptors on human lymphocytes. We have developed an indirect fluorescent method for detecting opioid binding sites. This method is more sensitive than radioreceptor binding methodology. Double labeling experiments using fluorescently tagged antibodies directed against specific CD cell surface markers and labeling the multiple opioid receptors with fluorescein-conjugated opioids, followed by an amplification procedure will result in determining which types of leukocytes express which type(s) of opioid receptors. Preliminary data demonstrate that the kappa receptor is expressed on the R1EGO thymoma cell line, on mouse thymocytes and splenocytes, and on CD4+ thymocytes. Similar experiments will be performed with mu and delta opioids labeled with fluorescein. The proposed experiments will result in a thorough characterization of the localization and relative number of the mu, delta and kappa receptors on mouse lymphocytes. Pharmacological evidence suggests that activation of T cells increases the expression of opioid receptors. Mouse thymocytes, macrophages and purified CD4+ and CD8+ cells will be activated and the receptor number and distribution will be compared to resting cells. These experiments will address whether activation of lymphocytes alters the expression of the opioid receptor and its distribution, and will help determine the function of the multiple opioid receptors on immune cells. Studies will be focused on determining if intravenous drug abuse, HIV infection and AIDS alters the expression or distribution of either mu, delta, or kappa opioid receptors. The proposed experiments will definitively determine which cells from the immune system express the classical opioid receptors and if drug abuse, HIV infection and AIDS alters the expression of these receptors.